Buggy code:
public class IssueUpdatesBuilder extends Builder { private static final String BUILD_PARAMETER_PREFIX = "$" ; private static final String HTTP_PROTOCOL_PREFIX = "http:////" ; private static final String HTTPS_PROTOCOL_PREFIX = "https:////" ; private static final String DELIMITER = "," ; private final String soapUrl ; private final String userName ; private final String password ; private final String jql ; private final String workflowActionName ; private final String comment ; private final String customFieldId ; private final String customFieldValue ; private String realJql ; private String realWorkflowActionName ; private String realComment ; private String realFieldValue ; private boolean resettingFixedVersions ; private String fixedVersions ; private boolean failIfJqlFails ; private boolean failIfNoIssuesReturned ; transient List < String > fixedVersionNames ; transient Map < String , Map < String , String > > projectVersionNameIdCache ; @ DataBoundConstructor public IssueUpdatesBuilder ( String soapUrl , String userName , String password , String jql , String workflowActionName , String comment , String customFieldId , String customFieldValue , boolean resettingFixedVersions , String fixedVersions , boolean failIfJqlFails , boolean failIfNoIssuesReturned ) { } public String getSoapUrl ( ) { } public String getUserName ( ) { } public String getPassword ( ) { } public String getJql ( ) { } public String getWorkflowActionName ( ) { } public String getComment ( ) { } public String getCustomFieldId ( ) { } public String getCustomFieldValue ( ) { } public String getFixedVersions ( ) { } public boolean isResettingFixedVersions ( ) { } public boolean isFailIfJqlFails ( ) { } public boolean isFailIfNoIssuesReturned ( ) { } @ Override public boolean perform ( AbstractBuild < ? , ? > build , Launcher launcher , BuildListener listener ) throws IOException , InterruptedException { } void substituteEnvVars ( Map < String , String > vars ) { } String substituteEnvVar ( String origin , String varName , String replacement ) { } private void updateFixedVersions ( SOAPClient client , SOAPSession session , RemoteIssue issue , PrintStream logger ) { } private Collection < String > mapFixedVersionNamesToIds ( SOAPClient client , SOAPSession session , String projectKey , Collection < String > versionNames , PrintStream logger ) { } private void updateIssueStatus ( SOAPClient client , SOAPSession session , RemoteIssue issue , PrintStream logger ) { } private void addIssueComment ( SOAPClient client , SOAPSession session , RemoteIssue issue , PrintStream logger ) { } private void updateIssueField ( SOAPClient client , SOAPSession session , RemoteIssue issue , PrintStream logger ) { boolean updateFieldSuccessful = false ; <START_BUG> if ( ! ( customFieldId . trim ( ) . isEmpty ( ) ) ) { <END_BUG> updateFieldSuccessful = client . updateIssueField ( session , issue . getKey ( ) , customFieldId , realFieldValue ) ; if ( ! updateFieldSuccessful ) { logger . println ( ( ( ( "Could<seq2seq4repair_space>not<seq2seq4repair_space>update<seq2seq4repair_space>field<seq2seq4repair_space>" + ( customFieldId ) ) + "for<seq2seq4repair_space>issue<seq2seq4repair_space>" ) + ( issue . getKey ( ) ) ) ) ; } } } @ Override public IssueUpdatesBuilder . DescriptorImpl getDescriptor ( ) { } @ Extension public static final class DescriptorImpl extends BuildStepDescriptor < Builder > { public FormValidation doCheckSoapUrl ( @ QueryParameter String value ) throws IOException , ServletException { } public FormValidation doCheckUserName ( @ QueryParameter String value ) throws IOException , ServletException { } public FormValidation doCheckPassword ( @ QueryParameter String value ) throws IOException , ServletException { } public FormValidation doCheckJql ( @ QueryParameter String value ) throws IOException , ServletException { } public boolean isApplicable ( Class < ? extends AbstractProject > aClass ) { } public String getDisplayName ( ) { } } }

Fix:
if ( ( ( customFieldId ) != null ) && ( ! ( customFieldId . trim ( ) . isEmpty ( ) ) ) ) {